The Mountain Hardwear Women"s Chiller Ball Cap is perfect for your next outdoor adventure while protecting you from the elements. Great for running, water sports, golf, and everyday casual wear. Made with wrinkle-resistant and quick-drying Summit Stretch Plainweave nylon fabric that is lightweight, breathable, and durable while providing UPF 50+ protection against harmful UV rays. Adjustable webbing and buckle on the back make for a comfortable, snug fit. Mesh panels promote airflow to keep your head cool and dry. Packs easily for travel. Wide brim for complete cover from the sun or rain. Underneath the brim is a dark color to reduce glare in your eyes. A closed cell foam brim keeps your hat afloat when you unexpectedly lose it overboard at the lake or river. Sizing (Head circumference): Regular: 21-22.25", Large: 23.75-25".